The primary objective of this proposal is to develop a novel upper extremity outcome measure for clinical trials in neuromuscular diseases (NMDs). An upper limb functional performance measure, unlike traditional measurement of static muscle strength or isolated joint range of motion, promises to be more sensitive to early changes in muscle function. Such an upper limb functional outcome measure could significantly shorten early phase clinical trials and hasten the therapeutic discovery process. With recent advances in 3-dimensional (3D) vision sensor technology, the study investigators were the first to develop an innovative yet simple, intuitive, low-cost methodology to quantitatively assess the 3D reachable workspace of the upper extremity using just one portable sensor system; essentially harnessing the capabilities of a full-scale motion analysis laboratory in a single sensor platform that provides comparably detailed 3D motion data. An upper extremity reachable workspace analysis is especially applicable to a variety of NMDs, since the typical pattern of weakness involves shoulder girdle muscles. This proposal builds upon the investigators' previous foundational work by extending the already developed methodology and software to a new commercially-available sensor platform (Microsoft Kinect) that promises to be accurate, cost-effective, and with greater potential for scalability and sustainability. In addition to healthy controls, the proposed study will test the developed system in two prototypical and common NMDs with shoulder girdle muscle weakness that will provide test-bed cases across the life spectrum and varying degrees of upper limb dysfunction: Duchenne muscular dystrophy (DMD) and Facioscapulohumeral dystrophy (FSHD). These represent both a rapidly progressive pediatric disease (DMD) and a slowly progressive late-onset disease process (FSHD). The specific aims are: 1) To determine the reliability and validity of the Kinect-measured upper limb reachable workspace against a simultaneously collected sub-millimeter full-scale motion analysis system's reachable workspace; 2) To determine the concurrent validity of Kinect-measured reachable workspace by evaluating against the other established measures of upper limb function including: Brooke scale, 9-hole peg test (9HPT), manual muscle testing (MMT), goniometry, and the NIH-developed NeuroQOL person reported outcome for upper limb function; and 3) To assess the responsiveness to change of the Kinect-measured reachable workspace during 1.5-year (18mo) longitudinal study with every 3 months data collection involving 40 DMD and 40 FSHD patients. The responsiveness to change of the Kinect's reachable workspace to disease progression will be compared against changes observed by traditional outcome measures. We will also examine Kinect-measured reachable workspace to predict loss of self-feeding as a clinically-meaningful milestone. Development of an accurate, reliable, cost-effective, and clinically-meaningful upper extremity outcome measure will significantly facilitate the therapeutic discovery process not only in NMDs but also for various other musculoskeletal conditions.